In the construction of various manmade projects such as roads and bridges, it is often necessary for the terrain around the project to be altered to accommodate a designed route. In hilly or mountainous terrain, traditional techniques for creating the route include earth moving and blasting efforts that can create very steep and unstable slopes. In the case of steep slopes that are cut from terrain with rock formations, the complete lack of soil can make it quite difficult for any vegetation to grow on the sloping surface such that significant soil erosion and the possibility of catastrophic collapse of the sloping surface is always a threat.
There a number of construction methods that have been employed to reduce soil erosion as well as to prevent catastrophic collapse of such sloping surfaces. For example, one method for preventing catastrophic collapse of a sloping surface is to create terraces on the sloping surface. Other techniques for preventing at least erosion of soil include the use of a geotextile mat anchored on the sloping surface.
One problem associated with efforts to stabilize a sloping surface is the cost associated with those efforts. Particularly for large cuts made in rocky terrain, extensive effort is required to properly terrace the slope. Additionally, geotextile material installed to prevent soil erosion further adds to the costs of the project.
Various state and national road construction standards require that sloping surfaces have a designated offset from the road to minimize the hazard of material sliding or falling onto the road. The standards also require stabilizing rock formations in the slope that could present a hazard to road users of the formation became unstable thereby allowing large rocks to fall. Even with these safety standards, soil erosion or more catastrophic soil and rock failures may be continual problems since it may take many years or even decades for adequate vegetation to grow on the sloping surface to stabilize the soil and rock.
Therefore, there is a need to provide a cost-effective, reliable, yet simple system and method for restoring natural vegetation to steep sloping surfaces.
In addition to preventing soil erosion, restoring natural vegetation to a sloping surface has environmental benefits such as the filtering of pollutants, recharging ground water, improving water quality, and restoring native ecosystems. The trend in both federal and state environmental quality standards increasingly requires that construction projects create minimal damage to the surrounding environment. Thus, an environmentally solution is also preferred with respect to stabilizing the sloping surfaces to meet these environmental standards.
With respect to using geotextile material to prevent soil erosion, geotextile material alone is ineffective on steep sloping surfaces, and particularly those steep sloping surfaces with rock formations. The geotextile material may fail in landslides or extreme erosion conditions since it has a limited material strength and is difficult to anchor to the slope. The geotextile material alone has little capability to stabilize the underlying geologic formation. Also, since use of geotextile material does not compensate for the lack of soil to adequately grow vegetation, even where geotextile material can be used, soil must be still present to grow the vegetation.